Roller bearings are capable of carrying high contact loads which result in high material stresses under running conditions. This applies also for the cages which are required to guide the rolling elements of the bearing in their right position. Therefore, attempts have been made to strengthen the ability of the respective parts of the bearing, particularly at or near the surface of the bulk bearing material; when lubrication conditions are poor improvements can be made by applying a coating of high load carrying capacity to the substrate material.
U.S. Pat. No. 6,340,245 B1 describes a roller bearing having an inner ring, an outer ring and rolling elements which are in rolling contact with the raceways of the rings. The rolling elements as well as the raceways of the rings are coated with a metal-mixed diamond-like carbon layer. Especially, the respective elements are coated with a metal-mixed diamond-like carbon coating comprising alternating layers of predominantly diamond-like carbon, but containing some metal carbide, and layers of predominantly metal carbide, but containing some of the diamond-like carbon.